Examples of a waveguide configured to transmit electromagnetic waves, i.e., particularly high-frequency signals such as microwaves, millimeter waves, or terahertz waves, include a hollow waveguide and a dielectric waveguide. Flexibility of a dielectric waveguide is better than flexibility of a hollow waveguide. As such a dielectric waveguide, there is known one having a structure in which a metal tape is helically wound up around the surface of a dielectric stick in order to increase flexibility without lowering transmission efficiency (for example, see Patent Document 1).
Patent Document 1: Japanese Patent Application Laid-open No. H08-195605